The present invention is related to the use of artificial lighting systems to promote plant growth, and more particularly, to the use of lighting systems to promote growth of plant tissue in cell well plates.
In biological and biochemical screening systems that employ plant tissue, it is important that the growth of the plant tissue be promoted. Growth of the plant tissue is affected by several factors which include the amount and type of nutrients supplied to the tissue, the physical support provided for the tissue, the temperature of the tissue environment and the amount of light delivered to the plant tissue. With respect to the availability of light, most screening systems employ artificial light which can be controlled and is not subject to the vagaries of the weather. In addition, the screening systems typically employ plates wherein each plate defines multiple wells. Each of the wells holds and isolates a separate tissue sample so as to avoid contamination with other tissue samples and the environment.
Existing systems for promoting plant tissue growth typically employ a rack, or xe2x80x9chotel,xe2x80x9d having multiple shelves each holding a plurality of the multiple well plates. Above each shelf is a bank of incandescent or fluorescent lights providing illumination to the multi-well plates and the tissue contained therein. The rack however, has a limited vertical stacking capacity as the lights must be kept a safe distance from the plant tissue to avoid excessive build-up of heat and because the incandescent and fluorescent lights are relatively bulky. Each shelf and light bank combination requires about one foot of vertical space, limiting a normal room with eight feet high ceilings to seven or eight shelves. In addition, incandescent or fluorescent lights are not very energy efficient, requiring about 4.4 watts of power per multiple well plate. Such large space and power requirements, coupled with cost constraints, tend to limit the density of the rack and the throughput of plant tissue screening systems.
Therefore, it would be advantageous to have a system for promoting the growth of plant tissues that can supply sufficient light to plant tissue in multiple well plates while also allowing for an increase in throughput of the screening operation. In particular, it would be advantageous to have a system for promoting the growth of plant tissues that does not occupy an excessive amount of space, nor require the use of large amounts of power per plate.
The present invention addresses the above needs and achieves other advantages by providing an assembly for promoting the growth of tissues requiring light to support proliferation. The assembly includes a plurality of plates each defining an array of wells wherein each of the wells contains one of the tissue samples and isolates its tissue sample from the other tissue samples. Support for the plates is provided by a rack having a plurality of vertically stacked shelves spaced a relatively short distance away from each other. Each of the shelves may include one or more register depressions that urge the plates resting thereon into predetermined positions. Light for the tissue samples is provided by a plurality of light-emitting diode arrays wherein each array is mounted on a circuit board. In turn, each circuit board is supported by a respective card edge connector of the rack so that the light-emitting diodes are in proximity to the plates supported on one of the shelves therebelow. Preferably, the light-emitting diode array corresponds to the well array supported in the registered position on the shelf therebelow so that each light-emitting diode is centered above a respective one of the wells.
In one embodiment, the present invention includes an assembly for promoting the growth of tissue samples requiring light to support proliferation. The assembly includes a plate defining therein a plurality of wells arranged in a well array. Each of the plurality of wells is configured to support and isolate one of the tissue samples. Further, the assembly includes a plurality of light-emitting diodes arranged in a light-emitting diode array. The light-emitting diode array corresponds to the well array such that each of the light-emitting diodes is positioned in proximity to a respective one of the wells so as to shine light into the respective one of the wells. Shining of light into the wells promotes proliferation of the tissue supported in the wells. Preferably, each of the light-emitting diodes is centered above its respective one of the wells. Further preferably, each of the light-emitting diodes emits a white light and is an inch or less from the tissue sample in its respective one of the wells.
In another embodiment of the present invention, a plurality plates and light-emitting diode arrays may be supported by a high-density rack. The rack includes a plurality of shelves vertically spaced from each other wherein each of the shelves is configured to support at least one of the plurality of plates. Each of the light-emitting diode arrays is supported by the rack above a respective one of the shelves. Light from the light-emitting diodes shines into the wells of the plate supported on the shelf below so as to promote tissue growth of the samples contained in the plate.
Preferably, each of the light-emitting diode arrays supported by the rack corresponds to the well array of the plate supported therebelow such that each of the light-emitting diodes is positioned above a respective one of the wells. In addition, the shelves of the rack can include register depressions which urge the plates disposed thereon into predetermined positions such that each of the light-emitting diodes is centered above its respective one of the wells. The rack may also include a plurality of card edge connectors that are each configured to receive a circuit board in which the light-emitting diodes are embedded to form a light-emitting diode array. The card edge connectors are positioned to support the circuit boards, and the light-emitting diodes embedded therein, above the shelves supporting the plates. Preferably, the shelves are less than two inches apart allowing a relatively high density of plates to be held by a rack even when vertical storage space is limited.
In yet another embodiment, the high-density rack may be employed with a manipulation system for use in high-throughput screening. The manipulation system includes a plate manipulator that has a range of motion. The rack is positioned so that the plates supported thereon are within the range of motion of the plate manipulator. The plate manipulator is then capable of supporting and removing each plate from the rack for automated processing, such as in a high-throughput sequencing operation.
The present invention has several advantages. The use of light-emitting diodes that are less bulky and emit less heat than fluorescent and incandescent bulbs allows the shelves of the rack to be more closely stacked. More closely stacked shelves increases storage efficiency by reducing the amount of space needed to house an adequate supply of tissue samples. This is particularly important in high-throughput screening operations where thousands of samples are needed on a daily basis. In addition, more plates are accessible to automated plate manipulators, such as robotic arms, that have a limited range of motion. Matching and alignment of each of the wells with its own light-emitting diode allows for calibration of the light beam spread and intensity for optimal tissue growth. Further, the light emitting diodes use light more efficiently and have lower power requirements for promoting tissue growth than fluorescent and incandescent bulbs, averaging about 1.3 watts per standard 4 by 6 plate compared to 4.4 watts for fluorescent and incandescent systems.